The bleaching compounds utilized by the types of over-the-counter teeth whitening products we discuss on our pages are:
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The majority of over-the-counter whitening products sold make use of either carbamide peroxide or hydrogen peroxide as their whitening agent.
Without question more research has been performed using 10% carbamide peroxide as an at-home whitener than any other type of peroxide compound. Unofficially 10% carbamide peroxide could be considered to be the standard for at-home teeth whitening, both in regards to safety and effectiveness. 10% carbamide peroxide was the whitener utilized by the original tray-based at-home teeth whitening system that gave rise to the explosion of over-the-counter whitening products found on the market today.
When utilized in the oral environment as a teeth whitener carbamide peroxide breaks down into the compounds hydrogen peroxide and urea at a ratio of about 3.5 to 6.5. This means that a 10% carbamide peroxide whitening gel will produce a bleaching solution that has a concentration of roughly 3.5% hydrogen peroxide. It is the compound hydrogen peroxide that produces the teeth whitening effect, the urea component does not participate in the bleaching process.
One reason carbamide peroxide is chosen as a whitener, as opposed to just using hydrogen peroxide itself, is related to the relative reactivity of these two peroxides. Carbamide peroxide is a more stable compound than hydrogen peroxide. This means that a carbamide peroxide whitening product can be counted on to have a more predictable shelf life than one composed of hydrogen peroxide. Shelf life considerations are important with over-the-counter products. A longer shelf life makes it easier for a company to deliver a predictably effective and safe product to consumers.
Another factor related to the use of carbamide peroxide as a teeth whitener is that it penetrates into tooth structure at a somewhat slower rate than hydrogen peroxide does and also is slower to release hydrogen peroxide to a tooth during the bleaching process. These properties can help to make an at-home product, where concerns about the end-user's precise compliance with instructions, more predictably effective and safe.
We feel it's important for you to realize why a teeth whitening product should have a neutral pH. When whiteners are used they are placed in direct contact with teeth for a prolonged period of time, for a number of successive treatment days. Since the exposed surfaces of teeth are mineralized tissues (tooth enamel and dentin) an acidic environment (of pH 5.5 and below) can etch mineral content from the teeth, possibly resulting in tooth damage.
The pH scale is a measure of a substance's acidity or alkalinity. It ranges from 0 to 14 with the lower end of the scale representing an acidic environment. Use of a teeth whitening product having a neutral pH (closer to the value of 7) would seem most prudent.
Please take notice of the fact that none of the descriptions of the various at-home teeth whitening methods we discuss on our pages makes any reference to the use of a pre-treatment rinse or an after treatment rinse. The need for either of these can imply that the pH of the technique is not neutral.
Pre-rinses utilized by over-the-counter whitening products are often acidic. The need for a neutralizing rinse after the whitening treatment has been completed implies that the whitener itself has an acidic pH.
In the early 1990's following a report of tooth damage related to the misuse of an over-the-counter teeth whitening kit containing an acidic pretreatment rinse, the Food and Drug Administration (FDA) considered changing the status of teeth whiteners from cosmetics (a type of product unregulated by the FDA) to drugs (products that the FDA does regulate). This led to a temporary ban of teeth whitening products in the fall of 1991 until June of 1992. The FDA ultimately decided not to reclassify teeth whiteners as drugs (and therefore today does not regulate these types of products).
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